The present invention is directed to semiconductor device packaging and, more particularly, to a flip chip die package having a copper pillar bumps interconnecting the die to a substrate.
Semiconductor device packaging fulfills basic functions such as providing electric connections and protecting the die against mechanical and environmental stresses. Continued progress in reduction of the size of the semiconductor dies and increased functionality and complexity of the electronic circuits integrated in the dies require size reduction of the packaging with the same or greater complexity of the electrical connections with external circuits.
Semiconductor devices are commonly packaged for surface mounting by encapsulating one or more semiconductor dies in an epoxy mould compound. Exposed electrical contacts for connection with external circuits are supported by the package and connected internally with electrical contact pads on the semiconductor die. Various techniques are available for connecting internally the exposed electrical contacts of the package with the embedded semiconductor die.
In a flip chip device, a die is mounted with its active face on a substrate, where conductive bumps formed on the die bonding pads are mated with contact pads on the substrate. The substrate includes wiring patterns and vias to route the electrical connections with the die to the external contacts on the opposite side of the substrate.
The bonding pads on the active face of the semiconductor die (or chip) may be metalized and solder balls applied to the contact pads, typically on the wafer, before the die is singulated (separated from adjacent dies). The singulated, bumped die is placed with its active face on the substrate and the then the solder bumps are re-melted, typically using an ultrasonic or alternatively a reflow solder process to establish the electrical connections. A minimum spacing of the solder balls is required to avoid risk of short circuits. A finer pitch and spacing of the die pads can be obtained using metal (for example copper) pillars or studs, with solder caps, which are grown on the die bonding pads. Conventionally, the pillars and solder caps are formed on the wafers before singulation of the dies. However, this process is very complicated and expensive.